Semi-submersible platforms have been widely used in oil and gas exploration/production as these mobile platforms may be moved easily from one site to another. However, as oil and gas explorations and operations move further offshore, various logistical problems arise. Particularly, offshore companies face logistical issues in transporting personnel and supplies to and from platforms located at remote locations or at sites that are located in severe environments. Typically, helicopters are used to transport personnel and supplies when such sites are located less than 150 km from the shore. However, such a transportation method becomes costly, risky and inefficient when the sites are located more than 300 km from the shore. Some typical problems associated with the use of helicopters for transportation to these remote sites include longer flights; the lack of nearby emergency response teams in the event of helicopter/vessel disasters; the lack of in-field servicing/refueling facilities; the lack of in-field storage/warehouse for storing foods and equipment; and the lack of accommodation facilities for personnel.
A solution to the above issues is to have a platform built halfway between the field site and the shore so that helicopters/vessels may be deployed to transport personnel from the shore to the platform, and subsequently to the intended field site. However, this method is still inefficient as the embarkation/disembarkation of personnel and the loading/unloading of materials between a vessel/helicopter and the platform are extremely difficult and dangerous under rough sea conditions. Therefore, under such severe conditions, it is a challenge to ensure that the platform remains stable with minimum motion.
A semi-submersible vessel is described in US Patent Publication No. 2003/0205189 A1 published on 6 Nov. 2003 in the name of Joe Wayne Key et al. This publication discloses a semi-submersible floating production vessel having a ring pontoon with several columns extending upwardly from the pontoon to support a deck on which production modules are positioned. The columns are surrounded with fenders for protecting the columns from impacts with floating bodies. It is an object of this publication to provide a semi-submersible vessel with sufficiently large water plane inertia to ensure adequate stability while minimizing the vessel motion response. It is not an object of this publication to provide a platform that serves as a logistics hub at a remote offshore location. Further, the design does not provide a docking area for ships that protects the ships from rough sea conditions.
A floating marine drilling structure for drilling wells in offshore locations is disclosed in GB Patent No. 1,065,216 published on 12 Apr. 1967 in the name of Laborde et al. This publication discloses a floating structure having a generally V-shaped hull configuration formed by a pair of triangular shaped hull wings. The V-shaped hull structure does not employ cross bracings between the main hull elements as it is disclosed that the hull wing configurations are able to resist the varying stresses acting on the structure. It is also disclosed that the floating structure has a high degree of stability under severe weather conditions as the centre of flotation is substantially coincident with the centre of the structure, where the two substantially triangular wings of the hull meet. The stability of this structure may be increased by increasing the size hull wings. However, as the sizes of the hull wings increase, the hull wings would be subject to higher torque and higher bending forces as the water plane area of the structure increases. In rough sea conditions, such forces could potentially be destructive.
A mooring arrangement for a floating body is disclosed in GB Patent No. 1,582,468 published on 7 Jan. 1981 in the name of Slotnaes. This publication describes a floating harbour installation that is in the shape of a horse shoe, V or U shaped for protecting docked vessels from rough weather. However, the arrangement disclosed in this document may be only be used close to shore or at locations where the base of the arrangement may be securely and fixedly moored to the sea bed.